node.js - Update And Return Document In Mongodb

Question

I want to get updated documents. This is my original code and it successfully updates but doesn't return the document.

collection.update({ "code": req.body.code },{$set:  req.body.updatedFields}, function(err, results) {
                        res.send({error: err, affected: results});
                        db.close();
                    });

I used the toArray function, but this gave the error "Cannot use a writeConcern without a provided callback":

collection.update({ "code": req.body.code },{$set:  req.body.updatedFields}).toArray( function(err, results) {
                    res.send({error: err, affected: results});
                    db.close();
                });

Any ideas?

Answer 1

collection.update() will only report the number of documents that were affected to its own callback.

To retrieve the documents while modifying, you can use collection.findOneAndUpdate() instead (formerly .findAndModify()).

collection.findOneAndUpdate(
    { "code": req.body.code },
    { $set: req.body.updatedFields },
    { returnOriginal: false },
    function (err, documents) {
        res.send({ error: err, affected: documents });
        db.close();
    }
);

The returnOriginal option (or new with Mongoose) lets you specify which version of a found document (original [default] or updated) is passed to the callback.

The returnDocument: "before" | "after" works for version 3.6.9.

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Disclaimer: This answer currently refers to the Node.js Driver as of version 3.6. As new versions are released, check their documentation for possibly new deprecation warnings and recommended alternatives.